Light emitting device

ABSTRACT

Provided is a light emitting device. The light emitting device includes: a plurality of lead frame units spaced apart from each other, each of the lead frame units being provided with at least one fixing space perforating a body thereof in a vertical direction; a light emitting diode chip mounted on one of the lead frame units; and a molding unit that is integrally formed on top surfaces of the lead frame units and in the fixing spaces to protect the light emitting diode chip.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.13/105,549, filed on May 11, 2011, which is a continuation of U.S.patent application Ser. No. 12/339,665, filed on Dec. 19, 2008, nowissued as U.S. Pat. No. 7,964,943, and claims priority from and thebenefit of Korean Patent Application No. 10-2008-0114624, filed on Nov.18, 2008, which are hereby incorporated by reference for all purposes asif fully set forth herein.

BACKGROUND

The present disclosure relates to a light emitting device, and moreparticularly, to a light emitting device that is configured to enhanceadhesive force between a lead frame and a molding unit by forming afixing space through the lead frame and integrally forming the moldingunit on the top surface of the lead frame and in the fixing space.

Generally, a light emitting device uses a variety of light emittingchips. For example, a light emitting diode (LED) uses an element thatgenerates minority carriers (electrons or holes) injected using a p-njunction of a semiconductor and emits light by recombination of thecarriers. The LED consumes less electricity and has several to tenstimes more service life than the incandescent light bulb or afluorescent lamp. That is, the LED is excellent in terms of the powerconsumption and endurance.

Since the LEDs can efficiently emit the light using a low voltage, theyhave been used for home appliances, electronic display boards, displaydevices, and a variety of automated machines. Recently, as the devicesare getting smaller and slimmer, the LEDs have been made in a surfacemount device type so that they can be directly mounted on a printedcircuit board. Particularly, a light emitting device that is designedsuch that a separate insulation substrate is not used but a lead frameis used instead of the insulation substrate and a molding unit isdirectly formed on the lead frame has been recently proposed.

However, there are limitations due to a structure of the molding unitformed only on a top surface of the lead frame in that a phenomenonwhere a boundary surface between the lead frame and the molding unit iswidened as the molding unit is easily separated from the lead frame byexternal causes such as increase of ambient temperature during a reflowprocess occurs.

Accordingly, the light emitting diode and wires enclosed by the moldingunit may be damaged by being exposed to air or moisture. In addition, abending portion may be cut by the separation of the molding unit.

SUMMARY

The present disclosure provides a light emitting device that is designedto physically improve adhesive force between a lead frame and a moldingunit by forming a fixing space through the lead frame and integrallyforming the molding unit on a top surface of the lead frame and in thefixing space during a molding unit forming process.

In accordance with an exemplary embodiment, a light emitting deviceincluding: a plurality of lead frame units spaced apart from each other,each of the lead frame units being provided with at least one fixingspace perforating a body thereof in a vertical direction; a lightemitting diode chip mounted on one of the lead frame units; and amolding unit that is integrally formed on top surfaces of the lead frameunits and in the fixing spaces to protect the light emitting diode chip.

The fixing spaces may include outer fixing holes that are formed at allor some of a region where the lead frame units face each other andopposite side edge regions of the lead frame units.

The fixing spaces may include at least one inner fixing hole formed inan inner region of the lead frame units.

Stepped portions may be formed on sidewalls of the fixing spaces spacesso that a lower portion area of the fixing space is greater than anupper portion area of the fixing space.

Inclined surfaces may be formed at the sidewalls of the fixing spaces sothat a lower portion area of the fixing space is greater than an upperportion area of the fixing space.

The light emitting device may further include a reflector formed on topsurfaces of the lead frame units and surrounding the light emittingdiode chip.

The molding unit may include a phosphor to alter a wavelength of lightemitted from the light emitting diode chip.

BRIEF DESCRIPTION OF THE DRAWINGS

Exemplary embodiments can be understood in more detail from thefollowing description taken in conjunction with the accompanyingdrawings, in which:

FIG. 1 is a perspective view of a light emitting device according to anexemplary embodiment;

FIG. 2 is a bottom perspective view of the light emitting device of FIG.1;

FIG. 3 a is a bottom view of a lead frame depicted in FIGS. 1 and 2;

FIG. 3 b is a bottom view of the light emitting device of FIGS. 1 and 2.

FIG. 4 is a perspective view of a light emitting device according toanother exemplary embodiment;

FIG. 5 is a bottom perspective view of the light emitting device of FIG.4;

FIG. 6 a is a bottom view of a lead frame depicted in FIGS. 4 and 5;

FIG. 6 b is a bottom view of the light emitting device of FIGS. 4 and 5;and

FIGS. 7 to 9 are cross-sectional views illustrating modified examples ofthe light emitting devices of the exemplary embodiments of FIGS. 1through 6 b.

DETAILED DESCRIPTION OF EMBODIMENTS

Hereinafter, specific embodiments will be described in detail withreference to the accompanying drawings.

FIG. 1 is a perspective view of a light emitting device according to anexemplary embodiment, FIG. 2 is a bottom perspective view of the lightemitting device of FIG. 1, FIG. 3 a is a bottom view of a lead framedepicted in FIGS. 1 and 2, and FIG. 3 b is a bottom view of the lightemitting device of FIGS. 1 and 2.

As shown in FIGS. 1 to 3 b, a light emitting device according to anexemplary embodiment includes a plurality of lead frame units 10, alight emitting diode chip 130 mounted on one of the lead frame units 10,and a molding unit 140 that is formed on a top surface of the lead frameunits 10 to protect the light emitting diode chip 130.

The lead frame units 10 are for mounting the light emitting diode chip130 or connected to the light emitting diode chip 130 to apply externalpower to the light emitting diode chip 130. In this exemplaryembodiment, a separate supporting unit such as a separate insulationsubstrate for supporting the lead frame units 10 is not provided, butthe lead frame unit 10 formed of metal functions as the substrate. Forexample, the lead frame units 10 include first and second lead frames110 and 120 that are spaced apart from each other at a predeterminedinterval. At this point, the first and second lead frames 110 and 120may not be formed in a plate shape but in a convex shape.

The first and second lead frames 110 and 120 are provided with fixingspaces formed through bodies of the first and second lead frames 110 and120 in a vertical direction.

When the molding unit 140 is formed on top surfaces of the first andsecond lead frames 110 and 120, molding resin for the molding unit 140is filled in the fixing spaces 20 such that the molding resin applied onthe top surfaces of the first and second lead frames 110 and 120 and themolding resin filled in the fixing spaces 20 can be monolithic. That is,the fixing spaces 20 function to allow the molding unit 140 to besecurely adhered to the top surfaces of the lead frame units 10.

As shown in FIGS. 1 through 3 b, the fixing spaces include outer fixingholes 111 and 121 that are formed at a region where the first and secondlead frames 110 and 120 face each other and a region surroundingopposite side edges of the respective first and second lead frames 110and 120. At this point, the outer fixing holes 111 and 121 may be someor all of the above described regions. In this exemplary embodiment, thefixing holes 111 and 121 are formed to be connected to each other at thefacing region where the first and second lead frames 110 and 120 faceeach other and the regions adjacent to the facing regions.

At this point, stepped portions 113 and 123 may be formed on sidewallsof the outer fixing holes 111 and 121 such that an area of a lowerportion of each of the outer fixing holes 111 and 121 is greater than anupper portion of each of the outer fixing holes 111 and 121. Therefore,the molding unit 140 formed on the top surfaces of the first and secondlead frames 110 and 120 extends to the outer fixing holes 111 and 121and is hooked on the stepped portions 113 and 123. Therefore, theseparation of the molding unit 140 from the first and second lead frames110 and 120 can be physically prevented. A method for making the lowerportion of the molding unit 140 formed in the outer fixing holes 111 and121 have a greater area than the upper portion of the molding portion140 is not limited to the above. That is, the method may be variouslymodified and the modified examples will be described later.

The light emitting diode chip 130 is for emitting light by receiving theexternal power. The light emitting diode chip 130 may be selected amongchips that emit light from an infrared band to a ultraviolet band. Thelight emitting diode chip 130 is mounted on the first lead frame 110 andelectrically connected to the second lead frame 120 by a wire 150. Thewire 150 may be formed of gold (Au) or aluminum (Al) through andconnected to the second lead frame 120 through, for example, a wireconnecting process.

The molding unit 140 is for protecting the light emitting diode chip 130and the wire 150 by enclosing the same. A method of forming the moldingunit 140 and a shape of the molding unit 140 can be variously realized.For example, the molding unit 140 may be formed through a transfermolding method where a mold having a cavity having a polygonal orhemispherical cavity and molding resin is filled in the cavity. In thisexemplary embodiment, the molding unit 140 is formed through a transfermolding method using a mold having a cavity that is designed to applythe molding resin on a portion of the top surfaces of the first andsecond lead frames 110 and 120 and fill the molding resin in the fixingholes 111 and 121. Therefore, the molding unit 140 is integrally formeda portion of the top surfaces of the first and second lead frames 110and 120, which includes a first region at which the light emitting diodechip 130 and the wire 150 are formed, a second region around the firstregion, and a third region defining the fixing space 20.

The molding unit 140 may be formed of transparent silicon resin or epoxyresin that has a relatively high rigidity. However, the presentinvention is not limited to this. That is, other kinds of resin that istransparent to transmit light may be used in accordance with the use ofthe light emitting device. Further, a variety of phosphors (not shown)may be mixed with the molding unit 140 to realize a variety of colors bychanging a wavelength of the light emitted from the light emitting diodechip 130.

FIG. 4 is a perspective view of a light emitting device according toanother exemplary embodiment, FIG. 5 is a bottom perspective view of thelight emitting device of FIG. 4, FIG. 6 a is a bottom view of a leadframe depicted in FIGS. 4 and 5, and FIG. 6 b is a bottom view of thelight emitting device of FIGS. 4 and 5.

The light emitting device of this exemplary embodiment is almostidentical to that of the foregoing embodiment of FIGS. 1 through 3 bexcept that the fixing spaces 20 are modified. In the followingdescription for this exemplary embodiment, parts identical to those ofthe foregoing exemplary embodiment will not be described.

Referring to FIGS. 4 through 6 b, according to this exemplaryembodiment, the fixing space 20 further includes one or more innerfixing holes 115 and 125 formed through the bodies of the first andsecond lead frames 110 and 120 in the vertical direction. Sizes, shapes,and number of the inner fixing holes 115 and 125 are not specificallylimited. Any things will be possible as far as the portions of themolding unit 140, which are filled and formed in the inner fixing holes115 and 125 are monolithic with the portion of the molding unit 140,which is formed on the top surfaces of the first and second lead frames110 and 120. In this exemplary embodiment, the inner fixing holes 115and 125 are formed in a variety of shapes such as a circular shape, anoval shape, and a rectangular shape. At this point, like the steppedportions 113 and 123 formed in the sidewalls of the outer fixing holes111 and 121 in the foregoing exemplary embodiment, stepped portions 117and 127 are formed on inner sidewalls of the inner fixing holes 115 and125 such that an lower area is greater than an upper area. Accordingly,the molding unit 140 is hooked on the stepped portions 113, 117, 123,and 127 and thus the separation of the molding unit 140 from the firstand second lead frames 110 and 120 can be prevented. are formed on innerwalls

Although the fixing spaces 20 include all of the outer fixing holes 111and 121 and the inner fixing holes 115 and 125 as in this exemplaryembodiment, it may be possible the fixing spaces 20 include only theinner fixing holes 115 and 125.

FIGS. 7 to 9 are cross-sectional views illustrating modified examples ofthe light emitting device of the foregoing exemplary embodiments.

The modified examples of FIGS. 7 to 9 are almost similar to theforegoing embodiments of FIGS. 1 through 6 a except that a reflector 160is further provided, the lead frame unit 10 is modified, and the fixingspaces 20 are modified. In the following description for the modifiedexample, parts identical to those of the foregoing embodiments will notbe described.

In the modified example of FIG. 7, a reflector 160 for collecting orscattering the light emitted from the light emitting diode chip 130 isformed on an edge of the top surfaces of the lead frame units 10. Atthis point, a reflecting surface is formed on an inner surface of thereflector 160 to direct the light emitted from the light emitting diodechip 130 in a desired direction. Alternatively, the reflector 160 may beformed of a transparent material to scatter the light generated from thelight emitting diode chip 130 in a desired direction.

The reflector 160 may be formed through the previously describedtransfer molding method. In addition, as the reflector 160 is formed,the molding unit 140 may be formed through not only the transfer moldingmethod but also a dotting method.

In the modified example of FIG. 8, unlike the foregoing embodiments, thelead frame units 10 include three lead frames spaced apart from eachother. For example, the lead frame units 10 may further include a thirdlead frame 170 disposed between the first and second lead frames 110 and120 and the light emitting diode chip 130 is mounted on the third leadframe 170. At this point, a contacting surface between the lightemitting diode chip 130 and the third lead frame 170 may be insulated.In addition, the light emitting diode chip 130 is electrically connectedto the first and second lead frames 110 and 120 by respective wires 150a and 150 b.

At this point, the outer fixing holes 111 and 121 and the inner fixingholes 115 and 125 are formed through the first and second lead frames110 and 120 and the stepped portions 113, 117, 123, and 127 are formedon the sidewalls of the outer and inner fixing holes 111, 121, 115, and125. Likewise, outer and inner fixing holes 171 and 175 are formedthrough the third lead frame 170 and stepped portions 137 and 177 areformed on sidewalls of the outer and inner fixing holes 171 and 175.Accordingly, the adhesive force between the molding unit 140 and thelead frame units 10 can be improved. Further, the reflector 160 may beformed on the fist and second lead frames 110 and 120.

In the modified example of FIG. 9, a shape of the fixing spaces isvaried. That is, instead of forming the stepped portions 113, 117, 123,and 127 on the sidewalls of the outer and inner fixing holes 111, 121,115, and 125 so that the lower area can be greater than the upper area,the inner sidewalls of the outer and inner fixing holes 111, 121, 115,and 125 are provided with inclined surfaces 118, 119, 128, and 129 suchthat the areas of the outer and inner fixing holes 111, 121, 115, and125 gradually increase downward. Although the inclined surfaces areformed on all of the inner sidewalls of the fixing spaces 20, thepresent invention is not limited to this configuration. That is, theinclined surfaces may be formed only on some of the inner walls.Accordingly, the separation of the molding unit 140 can be prevented byportions of the molding unit 140 that are filled and formed in the outerand inner fixing holes 111, 121, 115, and 125.

According to the exemplary embodiments, a phenomenon where a boundarysurface between the lead frame and the molding unit is widened can beprevented by improving an adhering performance of the molding unit tothe lead frame by forming the fixing space through the body of the leadframe in the vertical direction and integrally forming the molding uniton a top surface of the lead frame and in the fixing space of the leadframe.

Furthermore, as the upper area of the fixing space is less than thelower area of the fixing space, the separation of a portion of themolding unit, which is formed on the top surface of the lead frame, fromthe lead frame can be physically prevented by a portion of the moldingunit, which is formed on the fixing space.

Although the light emitting device has been described with reference tothe specific embodiments, it is not limited thereto. Therefore, it willbe readily understood by those skilled in the art that variousmodifications and changes can be made thereto without departing from thespirit and scope of the present invention defined by the appendedclaims.

What is claimed is:
 1. A light-emitting device, comprising: first andsecond lead frames spaced apart from each other, the first and secondlead frames each comprising a first surface, an opposing second surface,and sidewalls arranged between the first surface and the second surfacethereof, wherein the first and second lead frames each comprise threeinset sidewalls that at least partially define a fixing space, thefixing space undercutting the first surfaces along three sides of thefirst and second lead frames; a light-emitting diode chip arranged onthe first surface of the first or second lead frame; and a resin partdisposed in the fixing space to support the first and second leadframes.
 2. The light-emitting device of claim 1, wherein the firstsurface and the second surface of the at least one of the first andsecond lead frames comprise different surface areas from each other. 3.The light-emitting device of claim 1, wherein the inset sidewalls form astepped structure.
 4. The light-emitting device of claim 1, furthercomprising a reflector arranged on the first surface of each of thefirst and second lead frames, the reflector surrounding thelight-emitting diode chip.
 5. The light-emitting device of claim 1,wherein the resin part comprises a phosphor disposed therein.
 6. Thelight-emitting device of claim 1, wherein at least one sidewall of thefirst or second lead frame is inclined.
 7. The light-emitting device ofclaim 6, wherein the corresponding first and second surfaces havedifferent surface areas, due to the inclined sidewalls.
 8. Thelight-emitting device of claim 1, wherein the fixing space comprises afixing hole formed in at least one of the first and second lead frames.9. The light-emitting device of claim 8, wherein the fixing hole extendsthrough a body of at least one of the first lead frame and the secondlead frame.
 10. The light-emitting device of claim 8, wherein thesidewalls are inclined.
 11. The light-emitting device of claim 8,wherein at least one of the inset sidewalls comprises a concave portion,wherein the concave portion at least partially surrounds the fixinghole.
 12. A light-emitting device, comprising: first and second leadframes spaced apart from each other, the first and second lead frameseach comprising a first surface, an opposing second surface, andsidewalls arranged between the first surface and the second surfacethereof, wherein the first and second lead frames comprise insetsidewalls, the inset sidewalls undercutting and surrounding at leastthree continuous sides of the first surfaces of the first and secondlead frames, and at least one of the first surface, the second surface,and the sidewalls of the first and second lead frames partially defininga fixing space; a light-emitting diode chip arranged on the firstsurface of the first or second lead frame; and a resin part disposed inthe fixing space to support the first and second lead frames.
 13. Thelight-emitting device of claim 12, wherein the resin part ismonolithically disposed on the first surfaces of the first and secondlead frames, and in the fixing space.
 14. The light-emitting device ofclaim 12, further comprising a fixing hole formed in at least one of thefirst and second lead frames, and exposed to the fixing space at one ofthe inset sidewalls.
 15. The light-emitting device of claim 14, whereinthe sidewalls comprise stepped portions connected to the insetsidewalls.
 16. The light-emitting device of claim 15, wherein: thefixing space surrounds the at least three continuous sides of each ofthe first and second lead frames; and the fixing space is disposed in afacing region between the first and second lead frames.
 17. Thelight-emitting device of claim 16, wherein the resin part is disposed onthe first surfaces of the first and second lead frames, extends into thefixing space, and is hooked on the stepped portions.